These shackles need to be strong and completely reliable and yet manufactured as easily and as cheaply as possible. A particular area of difficulty lies in the securing into the shackle of the rotatably mounted eye which is to be semi-permanently attached to some part of the yacht and which therefore acts to retain the comparatively quickly-openable loop portion of the shackle.
Previous proposals for the securing of the eye have concentrated on ways of strongly fixing into a body of the shackle a separate bolt-like element which passed through an aperture in the eye part. This element was e.g. screwed into a screwed blind bore in the body, or passed into a blind bore and locked by a transverse dowel pin.
In an alternative approach, see U.S. Pat. No. 3,879,147, a head was secured, perhaps by welding onto an integral stem projecting outwardly from the body.
It can be seen that these proposals are undesirable from the point of view of manufacturing complexity and/or of reliability.